In recent years the development of OLED display panels is progressing with the aim of increased thinner, high luminosity and high speed display panels. These OLED panels are formed from pixels each of which is comprised from at least three organic compound light-emitting diodes (OLED light-emitting elements) which individually emit light of three colors (red, blue, green). Since the pixels do not contain any mechanical operations, they have a fast reaction speed and because each pixel itself emits light, high luminosity display is possible. In addition, because a backlight is unnecessary, a thin OLED display can be realized for next generation display panels.
These OLED display panels have a structure in which multiple OLED light-emitting elements corresponding to each pixel of an image to be display are formed in the shape of a matrix on a single substrate (glass substrate) and above this a transparent facing substrate is bonded for preventing light being emitted externally. Each OLED light-emitting element is comprised from a TFT (Thin Film Transistor) drive circuit layer, a reflection anode, a hole injection layer, a hole transport layer, an organic EL (Electro Luminescence) light-emitting layer, an electron transport layer, an electron injection layer, and a transparent cathode in this order from the substrate.
Among these, the organic EL light emitting layer which emits light is weak to heat since it is comprised from an organic material causing a change in its characteristic due to a peripheral temperature which is a significant problem. Therefore, conventionally a technology is proposed in which heat which is generated from a circuit (driver, circuit, register, power supply circuit etc.) for driving each OLED light-emitting element formed on an OLED display panel, or a TFT drive circuit forming the OLED light-emitting element, is controlled from being conducted to the organic EL light-emitting layer.
For example, a structure is conventionally proposed in which a heat diffusion sheet comprised from aluminum, copper or graphite is attached to the rear surface of an OLED display panel and heat generated on a circuit of one part is dissipated to the entire region of the OLED display panel via the heat diffusion sheet thereby preventing a high temperature section from being generated on a single part of the OLED display panel.
In addition, although patent document 1 (U.S. Pat. No. 4,553,991) is related to an LCD panel, a technology is proposed in which a conduction film comprised from a high melting point metal such as molybdenum for example is formed on the entire upper surface of a substrate in order to make the distribution of heat generated from a TFT or periphery circuit for driving each pixel uniform.
However, according to the technology of attaching a heat diffusion sheet to the rear surface of an OLED display panel, a separate process of attaching a heat diffusion sheet is necessary in addition to the manufacturing process of the OLED display panel and therefore processing costs for attaching the heat diffusion sheet in addition to the component costs of the heat diffusion sheet are necessary leading to high costs which is a problem.
In addition, even if the structure described in the patent document 1 is applied to an OLED display panel, the effects stop at uniformity of the heat distribution of the display panel and no consideration has been paid to heat dissipation externally. Therefore, the problem arises where heat accumulates across the entire display panel with time and finally the temperature of the organic EL light-emitting layer increases which is a problem.
In view of the above, the present invention attempts to provide an OLED display panel which easily dissipates heat generated from a circuit on the OLED display panel to the exterior using a structure which can rapidly reduce costs.